This invention relates to a beam processing system for processing a processing object by irradiating thereto a beam (particle beam) of light, electrons, ions or the like.
Referring to FIGS. 1A and 1B, a description will be given of an example of an ion implantation system, particularly a beam scan type ion implantation system, among beam processing systems. Such an ion implantation system is disclosed, for example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2003-288857.
In FIGS. 1A and 1B, ions produced in an ion source 301 are extracted as a beam 302 through a non-illustrated extraction electrode. The extracted beam 302 is subjected to a mass analysis in a mass analysis magnet device 303 so that a necessary ion species is selected. The beam 302 composed of the necessary ion species is shaped in cross section by a beam shaper 304. The beam shaper 304 is composed of a Q (Quadrupole)-magnetic pole lens, a Q electrostatic electrode lens, or the like. The beam having the shaped cross section is deflected by a deflection scanner 305 in a direction parallel to the sheet surface of FIG. 1A. Hereinafter, this direction will also be called a “scan direction” or a “lateral direction” and a direction perpendicular to such a direction will also be called a “vertical direction” or a “longitudinal direction”.
The deflected beam is parallelized again by a P (Parallel)-lens 306 so as to be parallel to an axis of a deflection angle of 0°. In FIG. 1A, a scan range of the beam by the deflection scanner 305 is indicated by a thick black line and a broken line at the downstreem side of the deflection scanner 305. The beam from the P-lens 306 is transferred to an angular energy filter 308 through one or more acceleration/deceleration electrodes 307. The angular energy filter 308 performs an analysis about energy of the beam to thereby select an ion species with necessary energy. As shown in FIG. 1B, the selected ion species is deflected slightly downward in the angular energy filter 308. The beam composed of the thus selected ion species is irradiated onto a wafer 310 through a plasma electron flood system 309. The beam that is not irradiated onto the wafer 310 is incident on a beam stopper 311 so that energy thereof is consumed. Normally, the structure from the ion source 301 to a vacuum process chamber where the wafer 310 is accommodated is called a beam line.
In this type of ion implantation system, the beam extracted from the ion source 301 performs, after the mass analysis, scanning in the lateral direction at a scanning frequency of several hundreds of Hz to several KHz by the deflection scanner 305 and then is parallelized by the P-lens 306. The longitudinal sectional shape (cross-sectional shape) of the beam is circular and the diameter size thereof is much smaller than the size of the wafer 310, but the beam scan range is set greater than the wafer 310. With respect to the vertical direction, i.e. the longitudinal direction, mechanical scanning is implemented to move the wafer 310. After the parallelization again, the beam is accelerated or decelerated by the acceleration/deceleration electrode or electrodes 307 so as to cover a wide energy range of 5 keV to 260 keV. By performing the energy analysis through the angular energy filter 308 in the form of an electric field or a magnetic field after the acceleration or deceleration, pure ions can be implanted into the wafer 310. Although not illustrated, energy slits are installed on the downstream side of the angular energy filter 308.
In this type of beam scan type ion implantation system, there is a case where the longitudinal sectional shape of a beam is required to be an elliptical or oval shape elongated in the scan direction, i.e. the lateral direction, for ensuring the uniformity of ion implantation into a wafer. In this case, the size of the longitudinal sectional shape is set smaller than the diameter of the wafer with respect to the beam width in the longitudinal direction but is set sufficiently greater than the diameter of the wafer with respect to the beam width in the lateral direction.